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Cardiac System
Material covered in class for cardiac exam
132
Physiology
Undergraduate 4
04/07/2013

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Term
what role does the heart play
Definition
pump, pressure head for blood flow
Term
what is pulmonary circulation
Definition
closed group of vessels carrying blood between heart and lungs
Term
what is systemic circulation
Definition
closed loop between heart and other tissues
Term
what are the 4 one way valves
Definition
right and left atriovascular valves; right and left semilunar valves
Term
what is the difference between the right and left atriovascular valves
Definition
right AV valve is tricuspid while left is bicuspid (mitral)
Term
what does the chordae tendineae do
Definition
anchors the flaps to prevent back flow in AV valves
Term
what do the right and left semilunar valves do
Definition
right separates right ventricle from pulmonary artery while left separates left ventricle from aorta
Term
what do gap junctions do in the heart
Definition
Allow propagation of action potentials between cardiac contractile cells
Term
what are characteristics of cardiac myocytes
Definition
striated, mostly single nucleus, branch, have intercalated discs
Term
what do the desmosomes do
Definition
resist pulling forces on cardiac myocytes
Term
are there are any gap junctions between cells of the atria and ventricles
Definition
the only place with gap junctions is in the AV node
Term
what is functional syncytia
Definition
the chemical, mechanical, and electrical connection between cardiac cells
Term
how many of the cardiac myocytes are contractile
Definition
99% are contractile
Term
how many of the cardiac myocytes are autorhythmic
Definition
1% are autorhythmic (noncontractile)
Term
what do the autorhythmic cells do
Definition
initiate and conduct APs
Term
what happens in pacemaker activity
Definition
membrane potential slowly depolarizes between AP’s; Repeated cycles of depolarization and repolarization
Term
what happens in the initial portion of the pacemaker potential
Definition
closing of K channels; opening of I-type Na channels with VG Na channels opening at relatively neg potential; results in modest Na influx
Term
what happens in the latter portion of the pacemaker potential
Definition
F-type Na channels close; Transient Ca channels open (Ca influx depolarize to thresh); at thresh T-type Ca channels close, long-lasting (L) Ca VG channels open until peak potential reached; L-Ca channels close, VG K channels open, depolarization; repeat process
Term
what are the main parts of the cardiac conduction system
Definition
SA node, AV node, bundle of His (AV bundle), purkinje fibers
Term
what is the sinoatrial node (SA)
Definition
small specialized region near opening of superior vena cava
Term
what is the atrioventricular node (AV)
Definition
region at base of right atrium near septum and junction between atria and ventricles; Only electrical connection between atria and ventricles
Term
what is the bundle of his
Definition
Originates at AV node and enters interventricular septum; Left and right bundle branches and Travel down septum and curve around back toward atria along the ventricular wall
Term
what are purkinje fibers
Definition
small terminal fibers that extend from bundle branches and terminate throughout the myocardium
Term
list the conduction system from strongest pacemaker activity to weakest activty
Definition
SA, AV, purkinje
Term
what is the path of depolarization in the heart
Definition
SA node, through internodal pathway into AV node (delayed here), through interatrial pathway into left atrium, throughout contractile myocytes of atrium, into bundle of his, through purkinje fibers, into contractile ventricular myocytes
Term
when does ventricular contraction occur
Definition
after atria go through excitation and contraction
Term
what causes ventricular filling
Definition
80% is passive filling; 20% is a result of atrial contraction
Term
how do the muscle fibers excite when compared to each chamber
Definition
fibers should be excited such that each chamber has coordinated simultaneous contraction
Term
what is fibrillation
Definition
Uncoordinated excitation/constriction of cardiac myocytes
Term
what is defribillation
Definition
application of electrical current to cause all cardiac cells to depolarize in hope that SA node resumes pacemaking
Term
how should atria and ventricles contract
Definition
atria should contract simultaneously and ventricles should contract simultaneously
Term
what are three types of abnormal pacemaker activity
Definition
latent pacemaker, complete heart block, ectopic focus
Term
what happens in latent pacemaker
Definition
a non-SA node autorhythmic cell takes over as pacemaker
Term
what happens in complete heart block
Definition
AV node is nonfunctional; no electrical connection between atria and ventricles; ventricular depolarization driven by purkinje fibers
Term
what happens in ectopic focus
Definition
rapid depolarization of region other than SA node; may take over and lead to inappropriate rapid contraction
Term
how do cardiac contractile cells
Definition
impulse originates at SA node, spreads cell to cell through gap junctions, initial depolarization to threshold, leaky K channels open, spread of current from adjacent excited cells bring Vm to threshold, at threshold VG Na channels open, at peak Na channels close and Transient K channels and close quickly, L-type Ca channels open leading to plateau phase, ordinary VG K channels open at end of plateau phase to repolarize, at rest the VG K channels close but leaky K channels open
Term
what is the plateau phase
Definition
a prolonged depolarization caused by Ca influx when L-type Ca channels open
Term
where are L-type Ca channels in cardiac myocytes
Definition
located in T-tubules
Term
where does the Ca come from
Definition
from ECF and then initiates release of more Ca from SR
Term
What does the increase in cytosolic Ca do
Definition
Ca binds to troponin; increases force of cardiac contraction
Term
what happens to Ca during cardiac relaxation
Definition
Ca is removed from cytosol; Ca ATPase pumps sequester Ca into SR; 2 active transport at PM move Ca into ECF
Term
Why do cardiac myocytes have long refractory periods
Definition
it is due to prolonged depolarization of the plateau phase which does not allow for twitch summation or tetanus
Term
What is a ECG
Definition
a recording of the electrical activity of the heart that reaches the body surface
Term
what are the different parts of the ECG
Definition
P-wave; QRS complex; PR segment; T-wave; ST segment; TP interval
Term
what is associated with the P-wave in the heart
Definition
depolarization of the atrium
Term
what is associated with the QRS complex in the heart
Definition
depolarization of ventricles
Term
what is the PR segment
Definition
it is the combined P-wave and QRS complex with AV nodal delay
Term
what is associated with the T-wave in the heart
Definition
ventricular repolarization
Term
what is associated with the ST segment in the heart
Definition
the time when ventricles are contracting and emptying
Term
what is associated with the TP interval in the heart
Definition
muscle is completely at rest and ventricular filling is taking place
Term
what is tachycardia
Definition
elevated heart rate above 100bpm
Term
what is bradycardia
Definition
heart rate below 60bpm
Term
what is systole
Definition
period of contraction
Term
what is diastole
Definition
period of relaxation
Term
what is Fig 9-16
Definition
THE CARDIAC CYCLE (GO STUDY NOW)
Term
when is the first heart sound heard (lub)
Definition
during ventricular excitation/ onset of ventricular systole when the AV valve closes
Term
when is the second heart sound heard (dub)
Definition
during ventricular repolarization; the SL valve closes
Term
what is cardiac output
Definition
volume of blood pumped by each ventricle per minute (ml/min)
Term
how does the CO of the left and right ventricles compare
Definition
both sides are generally equal
Term
what is the equation for CO
Definition
stroke volume*HR
Term
what is heart rate (HR)
Definition
rate of SA node depolarization
Term
how is HR controlled
Definition
intrinsic rate of SA node depolarization; parasympathetic effects; sympathetic effects
Term
how does the parasympathetic effect HR
Definition
Muscarinic receptors for Ach at SA node; Increased K perm at SA fibers slowing pacemaker potentials; increase in AV nodal delay
Term
how does the sympathetic effect HR
Definition
Release of NE from neuron (EPI from adrenal medulla) which binds to B1 receptor which causes steeper/quicker pacemaker potentials; augmentation of Na and Ca T-type channels which leads to increase of depolarizations/min and decrease in AV nodal delay
Term
what is stroke volume dependent on
Definition
on length-tension; increased fiber length= more forceful contractions; Frank-Starling law of heart
Term
what are the two types of controls in stroke volume
Definition
intrinsic controls (Frank-Starling Law); extrinsic controls (Autonomic nervous system)
Term
what do longer muscle fibers result in
Definition
the thick and thin filaments are closer together; more cross bridge interactions in a longer fiber
Term
what does the Frank-Starling law of the heart show
Definition
increasing EDV increases SV
Term
what are the parasympathetic effects on stroke volume
Definition
decreased contractility in atria; little to no effect on contractility in ventricles
Term
what are the sympathetic effects on stroke volume
Definition
increases contractile strength in atria and ventricles; increases permeability of Ca leading to increase in Ca in cytosol to be used for contraction
Term
what is flow rate
Definition
vol of blood passing per unit of time
Term
what is flow directly proportional to
Definition
delta P/resistance
Term
what is delta P
Definition
it is pressure gradient directly proportional to flow difference between beginning and end
Term
what is Flow inversely proportional to
Definition
resistance
Term
what causes increased resistance
Definition
increased viscosity and decreased radius (radius has stronger effect), increased friction, increased surface area
Term
how much of an effect does radius have
Definition
resistance=1/r^4
Term
what is resistance proportional to
Definition
current/radius^4
Term
what is Pouirelle's Law
Definition
Flow rate= (pi* delta P* r^4)/(8*viscosity*length)
Term
how does blood flow through arteries
Definition
systole: stroke volume enters the arteries
Diastole: no blood enters arteries from the heart
Elastic Recoil
Term
what does elastic recoil do
Definition
provides the pressure to propel blood into arterioles
Term
how do pressures compare in arteries
Definition
Systolic pressure > than diastolic pressure
Term
how is mean arterial pressure (MAP) calculated
Definition
MAP= diastolic pressure + (Pulse Pressure/3)
Term
what are arterioles
Definition
major resistance vessels with high degree of resistance causing drop in pressure as blood flows through; also diminishes pulsatile nature of pressure
Term
what does arteriolar radii adjustment do
Definition
Variable distribution of cardiac output (CO); Regulation of arterial pressure
Term
what is the vascular tone in arterioles
Definition
normally a tonic level of vasoconstriction
Term
what type of controls for vascular tone are in arterioles
Definition
myogenic and neurogenic
Term
what intrinsic controls are used to increase CO/increase vasodialation
Definition
increase temp; increase CO2; decrease O2; Decrease pH(increase Lactic acid and carbonic acid); Increase in local [K]; Increase osmolarity; Increase in nitric oxide (powerful vasodilator)
Term
what is resistance proportional to
Definition
current/radius^4
Term
what is Pouirelle's Law
Definition
Flow rate= (pi* delta P* r^4)/(8*viscosity*length)
Term
how does blood flow through arteries
Definition
systole: stroke volume enters the arteries
Diastole: no blood enters arteries from the heart
Elastic Recoil
Term
what does elastic recoil do
Definition
provides the pressure to propel blood into arterioles
Term
how do pressures compare in arteries
Definition
Systolic pressure > than diastolic pressure
Term
how is mean arterial pressure (MAP) calculated
Definition
MAP= diastolic pressure + (Pulse Pressure/3)
Term
what are arterioles
Definition
major resistance vessels with high degree of resistance causing drop in pressure as blood flows through; also diminishes pulsatile nature of pressure
Term
what does arteriolar radii adjustment do
Definition
Variable distribution of cardiac output (CO); Regulation of arterial pressure
Term
what is the vascular tone in arterioles
Definition
normally a tonic level of vasoconstriction
Term
what type of controls for vascular tone are in arterioles
Definition
myogenic and neurogenic
Term
what intrinsic controls are used to increase CO/increase vasodialation
Definition
increase temp; increase CO2; decrease O2; Decrease pH(increase Lactic acid and carbonic acid); Increase in local [K]; Increase osmolarity; Increase in nitric oxide (powerful vasodilator)
Term
what does NO do
Definition
Potent vasodilator; Inhibits Ca entry into smooth muscle; Relaxation
Term
what does endothelin do
Definition
released by endothelial cells; potent vasoconstrictor
Term
what does Vascular endothelial growth factor (VEGF) do
Definition
Chronic hypoxia; Stimulates angiogenesis; Growth of new blood vessels
Term
what does histamine do
Definition
Released from immune cells in response to injury; Part of the inflammation reaction; Vasodilator
Term
what physical factors affect stretch
Definition
Heat-->vasodilation
Cold-->vasoconstriction
Term
what happens if MAP is increased
Definition
vessel walls stretch; smooth muscle contracts; vasoconstriction
Term
what does sympathetic nervous system innervate
Definition
all arteriolar smooth muscle except in brain
Term
what happens if NE binds to alpha receptors
Definition
vasoconstriction; Increase in resistance (R), and increase in BP
Term
what happens if EPI binds to B2 receptors
Definition
vasodilation in addition to metabolic conditions that favor vasodilation
Term
what does parasympathetic innervation cause
Definition
vasodilation in sexual tissues
Term
what does vasoprassin do
Definition
production of concentrated urine, “water conservation”; vasoconstrictor
Term
what is the role of capillaries
Definition
exchange of material
Term
what are characteristics of capillaries
Definition
small (7um); lots of branching; large cross-sectional area; very slow velocity of flow
Term
how does exchange work in capillaries
Definition
diffusion down concentration gradients; pores between cells; vesicular transport; precapillary sphincters
Term
what diffuses through pores in capillaries
Definition
small water soluble substances (glucose, ions, amino acids)
Term
how does vesicular transport work in capillaries
Definition
it regulates some specific proteins; plasma proteins stay in capillary
Term
how do precapillary sphincters work
Definition
Relaxed when conditions indicate an increase in cellular respiration; Contracted when indications decrease cellular respiration
Term
what is bulk flow
Definition
Pressures favor movement of fluid out of cap at the arteriolar end into cap at venule end
Term
what is hydrostatic pressure
Definition
the force of fluid pushing up against a wall
Term
what is colloid osmotic Pressure/Oncotic Pressure
Definition
pressure due to presence of nonpermeating solutes
Term
how is Net exchange pressure (NEP) calculated
Definition
NEP=(Pc + πif)-(πp+Pif)
= (outward) - (inward)
Term
where does excess fluid return? How?
Definition
returned to circulatory system by lymphatic vessels
Term
what causes liver failure
Definition
Decrease plasma protein; Decreases πP; Cause Edema
Term
what are venules
Definition
smallest of venous system; capillaries drain into venules; venules combine into veins
Term
characteristics of veins
Definition
thinner walls than arteries; blood reservoirs; adaptations to flow in low pressure conditions
Term
what are adaptations that veins have for flow in low pressure conditions
Definition
Wide lumen: reduces resistance; One-way valves found in veins of limbs; Muscular pump; Contraction of surrounding skeletal muscle
Term
what is the respiratory pump
Definition
Pressures in ventral cavity create a pump that moves blood toward heart; Inhalation: abdominal vessels are squeezed which increases pressure; Thoracic vessels have decreased pressure, which creates gradient that favors blood flow back to heart
Term
what happens during ventricular contraction
Definition
the AV-valves dip inward; volume of atrium expands; decrease pressure below zero to favor venous return
Term
what is a short-term regulation of BP
Definition
Baroreceptor reflex
Term
characteristics of baroreceptor reflex
Definition
responds to changes in MAP and pulse pressure; mechanoreceptors; in aortic arch and carotid sinus
Term
what does increasing MAP cause
Definition
increase in receptor potential leading to increase in frequency of APs in afferent neuron
Term
what is the integrator
Definition
the cardiovascular control center; the medulla (brain); decreases symp activity and increases parasymp activity
Term
what are ways of long-term regulation of blood pressure
Definition
control of blood volume; volume receptors and osmoreceptors regulate water and salt balance to control blood volume (increase blood volume= increase MAP)
Term
what does increased venous return cause
Definition
increase in SV which causes increased EDV
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